Envelope Generator



An Envelope Generator (EG) is a device for creating a contoured CV from an 'on/off' CV source (generally a Gate or Trigger). Effectively an envelope is a type of waveform not usually considered as a wave - mostly because it is generally used to shape or 'contour' other signals, and not necessarily repeating in a cyclic manner such as the wave an oscillator would produce. In other words, an envelope generally creates a CV that rises, falls and can be held at a particular voltage for defined lengths of time so as to sweep through and shape other parameters of a modular synth such as amplitude, pulsewidth or filter cuftoff frequency etc.

The classic Envelope Generator in most synths is an ADSR (Attack, Decay, Sustain, Release) contour shaper:
 * The 'Attack' setting defines the time taken for the CV signal to rise from it's initial 0V to the maximum output voltage,
 * The 'Decay' setting defines the time taken for the CV signal to fall from the maximum voltage to the sustain level,
 * The 'Sustain' setting defines the level the CV signal holds at as long as the gate signal remains present (i.e. the envelope doesn't define a time for this setting, just a voltage level, the gate signal defines this time),
 * The 'Release' setting defines the time taken for the CV signal to fall from the sustain level bacl down to a zero output voltage.

Do be aware though, an Envelope Generator contour can be as simple as a rise and fall, triggered by a gate or trigger signal, through to a complex sequence of rise, fall, hold/sustain and off sections in a cycling fashion acting as an intricately shaped LFO. There are even EGs that will invert the envelope either across a range of depths, or from separate outputs, so as to provide fall, then rise, then sustain, then release going from a full signal to no signal at all and then back up. to complicate things further there are also generators that will add pre-delay, re-trigger, one-shot trigger, gated repeats and hold functions to name but a few...